Binocular see-through configuration and eye movement attenuate visual rivalry in peripheral wearable displays

Abstract

Visual confusion occurs when two dissimilar images are superimposed onto the same retinal location. In the context of wearable displays, it can be used to provide multiple sources of information to users on top of the real-world scene. While useful, visual confusion may cause visual rivalry that can suppress one of the sources. If two different images are projected to each eye (i.e., monocular displays), it provokes binocular rivalry wherein visual perception intermittently switches between the two images. When a semi-transparent image is superimposed (i.e., see-through displays), monocular rivalry results, causing perceptual alternations between the foreground and the background images. Here, we investigated how these rivalries influence the visibility of the peripheral target using three configurations of wearable displays (i.e., monocular opaque, monocular see-through, and binocular see-through) with three eye movement conditions (i.e., saccades, smooth pursuit, and central fixation). Using the HTC VIVE Eye Pro headset, subjects viewed a forward vection of a 3D corridor with a horizontally moving vertical grating at 10° above the center fixation. During each trial (~1 min), subjects followed a fixation cross that varied in location to induce eye movements and simultaneously reported whether the peripheral target was visible. Results showed that the binocular display had significantly higher target visibility than both monocular displays, and the monocular see-through display had the lowest target visibility. Target visibility was also higher when eye movements were executed, suggesting that the effects of rivalry are attenuated by eye movements and binocular see-through displays.

Keywords: See-through display; augmented reality; binocular/monocular rivalry; eye movements; mobility; peripheral head-mounted display; wearable display.

Figure 1.

Stimuli and experimental procedure. (a) The peripheral target was a 1 cycle per degree horizontally moving grating and the background was a 3D forward vection tunnel. To simulate the different display configurations, the target was either set to an alpha level of 1.0 or 0.5. (b) The procedure during each trial is illustrated. During the stimulus presentation phase, subjects were tasked to track the visibility of the peripheral target while following the fixation cross, which remained at a fixed location or varied across time.

Figure 2.

Gaze accuracy. (a) Group mean gaze errors (degrees in visual angle) across conditions. On average, subjects made significantly smaller gaze errors in fixation condition (1.3° ± 0.1° SD) compared to when eye movements were executed (1.67° ± 0.16° SD for saccade; 1.68° ± 0.15° SD for smooth pursuit). There was no noticeable difference in mean gaze error across different display types. Dots represent individual data. (b) Example of gaze for different eye movement conditions in one subject. Solid lines represent the horizontal (left) and vertical (right) positions of the fixation point throughout one trial for each eye movement condition. The subject’s gaze location is plotted in a dotted line.

Figure 3.

Effect of display configuration on target visibility. Average target visibility for each display configuration is represented with a filled marker. Target visibility was higher in binocular see-through display compared to both monocular opaque and monocular see-through displays. In all display configurations, the target was more visible when eye movements were executed than when the eyes were fixated at the center. Error bars represent 95% confidence intervals.